Saw blade having liquid transport cavity for use with lubricating guide support assembly

ABSTRACT

A saw arrangement includes the combination of a circular saw blade and a lubricating guide support assembly. The circular saw blade includes a saw plate having openings formed therein and carbide insert teeth disposed circumferentially about the saw plate. The lubricating guide support assembly includes two guide supports each having a bearing surface disposed immediately adjacent opposite sides of the saw plate at a spacing to the cutting area for proper alignment of the saw blade during cutting. At least one of the guide supports includes a recessed area containing liquid exposed to the saw plate whereat a thin film of the liquid is applied to the saw plate as it passes by the recessed area during cutting. The openings are arranged on the saw plate to pass by the recessed area and are dimensioned to receive liquid therein for transport away from the recessed area. When each opening clears the bearing surfaces of the guide supports the liquid transported therein is distributed to the saw plate and the cutting area including the carbide insert teeth by air turbulence and inertial forces. Such a saw blade having a thickness at least as small as 0.080 inches is used to cut lumber from Southern Yellow Pine.

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a continuation of International ApplicationNo. PCT/US00/00365, filed Jan. 7, 2000, which was published in Englishunder PCT Article 21(2) which is incorporated herein by reference andwhich, in turn, claims the benefit of the filing date of U.S. patentapplication Ser. No. 09/232,401, filed Jan. 15, 1999, now U.S. Pat. No.6,050,163, which also is incorporated herein by reference.

FIELD OF THE PRESENT INVENTION

[0003] The present invention relates to a saw arrangement and, inparticular, to a saw blade having a liquid transport cavity for use witha lubricating guide support assembly.

BACKGROUND OF THE PRESENT INVENTION

[0004] Saw blades are commonly used to cut raw materials intointermediate or final products, and as the width of the saw blade isdecreased, more product can be cut generating higher productivity. As anexample, a simple arrangement of circular saw blades mounted on an arborwere once often used to cut pieces of lumber. In such arrangements whichwere used for cutting Southern Yellow Pine, the typical width of eachcircular saw blade was approximately 0.180 inches.

[0005] An improvement that was made in this simple arrangement is theprovision of a guide support assembly comprising two guide supports withopposed bearing surfaces for maintaining proper alignment of eachcircular saw blade therebetween during cutting, thereby permitting thereduction of the thickness of the saw blade to dimensions that wouldhave otherwise compromised cutting alignment. The guide support assemblyis required because the circular saw blades have been reduced to athickness rendering them incapable of maintaining a generally planarconfiguration during cutting, thereby making them unsuitable for usewithout auxiliary side support. Unfortunately, as saw blade thicknessdecreases more support must be provided by the bearing surface of theguide support against the saw blade which generates greater frictiontherebetween. This increase in friction can lead to excessive heating ofthe saw blade which, in turn, can ultimately lead to carbide insertteeth breakage, sawing deviation, guide pad wear, and saw blade damage.

[0006] Further improvements to this saw arrangement were made in thelate 1980's. In a first improvement, cooling of the saw blade isaccelerated by the provision of circumferential air slots throughout thesaw body, of which the saw blade disclosed in Carter Jr. U.S. Pat. No.4,776,251 is representative. In Carter Jr. a circular saw blade isdisclosed having slots cut in the body thereof using a laser. Each slotconsists of an arc of a circle concentric with the saw body and parallelto the peripheral edge of the saw body. The radial width of the slot isselected to be between 0.002 and 0.015 inches and remains constant inthe circumferential direction of the saw body between opposedcircumferential ends of the slot. The common problem of sawdust packingin similar openings formed in a saw body, as disclosed for example inJansen-Herfeld U.S. Pat. No. 4,574,676 and as expressly discussed byCarter Jr. at cols. 3-4, is avoided in the circular saw blade of CarterJr. because of the limitation on the radial width of each slot to lessthan 0.015 inches and because of the disposition of the slots in acircumferential direction with no radial component. Furthermore, unlikethe blade disclosed in Jansen-Herfeld, the circular saw blade of CarterJr. can be used with guide supports without damaging the bearingsurfaces thereof due to the narrowness of each slot and itscircumferential arrangement. In this arrangement, the plurality of slotsprovide a radiator cooling effect that accelerates cooling of the sawblade but the slots fail to reduce any friction generated between thesaw body and the bearing surface of the guide supports.

[0007] In a second, independent improvement to the saw arrangementhaving guide supports, an actual reduction of the friction between thesaw blade and the guide supports is accomplished by the applicationwithin each guide support of a lubricating liquid to the saw body. Aconventional saw arrangement including a representative illustration ofthis improvement is disclosed in McGehee U.S. Pat. No. 4,848,200. Inthis saw arrangement a mixture of oil and water is applied to a saw bodyof a circular saw blade as it passes by guide supports retaining the sawblade in proper cutting alignment. Typically the liquid is delivered toa recessed opening in each guide support under a pressure of 35 psi andthe guide support is maintained immediately adjacent the saw body at agap of between 0.001 and 0.003 inches, whereby a thin film of liquid isapplied to the saw body as it passes thereby. The application of alubricating liquid reduces friction—and thus heat—generated between theguide supports and the saw body.

[0008] As a result of such improvements in saw arrangements having guidesupport assemblies, the conventional thickness of a saw blade in a sawarrangement used to cut Southern Yellow Pine has been reduced from 0.180inches to 0.080 inches. Nevertheless, a need has arisen in recent yearsto reduce the thickness of a circular saw blade for cutting SouthernYellow Pine still further as demand for greater productivity in lumbermills has arisen. Such attempts at thinner saw blades generally havebeen unsuccessful due to insufficient cooling and consequentoverheating, and better cooling techniques must be developed to advancethis sought-after reduction in saw blade thickness.

SUMMARY OF THE PRESENT INVENTION

[0009] The present invention exhibits improved cooling of a saw bladeretained in proper cutting alignment by lubricating saw guide supports,thereby advancing attempts to reduce saw blade thickness. In particular,the present invention, when used to cut Southern Yellow Pine, has beenfound (among other advantages): to provide less maintenance thanconventional saw blades; to provide less entailed maintenance operationswhen maintenance is required than that of conventional saw blades; andto provide a longer operating life than conventional.

[0010] Briefly described, the present invention relates to a sawarrangement comprising the combination of a saw blade and a lubricatingguide support assembly including two guide supports having opposedbearing surfaces for maintaining the saw blade in proper cuttingalignment therebetween. The saw blade includes a saw body that defines acavity therein and a cutting edge disposed along a periphery of the sawbody for cutting during movement of the saw blade. Each guide supportincludes the bearing surface being disposed immediately adjacent the sawbody for support of the saw blade during cutting as well as alubricating system comprising a recessed area extending from the bearingsurface and containing liquid exposed to the saw body, whereby theliquid is applied to the saw body as it passes by the recessed areaduring movement of the saw blade.

[0011] In a feature of the present invention, the cavity is arranged onthe saw body to pass by the recessed area during movement of the sawblade and is dimensioned to receive liquid therein for transport awayfrom the recessed area to be distributed to the saw body as well as acutting area of the saw blade. Preferably, the saw blade is circular,and the saw body is planar and includes three cavities disposed relativeto one another at 120 degrees about the center of the saw blade. Eachcavity is triangular in cross-section and extends from a first planarside of the saw body to a second planar side thereof. Also, each cavitypreferably includes only rounded corners, and each cavity preferably hasa radial dimension that varies along a circumferential direction of thecircular saw blade between opposed circumferential ends of the cavity.

[0012] The present invention also relates to a method of using acircular saw blade itself with a lubricating guide support assembly tocut lumber from Southern Yellow Pine. In particular, the circular sawblade includes a planar saw body having an axial thickness of no greaterthan 0.080 inches and defines a cavity therein having a radial dimensionthat varies along a circumferential direction of the circular saw bladebetween opposed circumferential ends of the cavity. The cavity itselfpreferably includes a radial dimension greater than 0.015 inchessufficient to receive liquid therein when passing by a recessed area ofa lubricating guide support.

[0013] The present invention further relates to a method fordistributing lubricating and cooling liquid to a cutting area of a sawblade used in combination with a lubricating guide support assembly. Inparticular, the method includes the steps of delivering liquid into arecessed area of the lubricating guide support, filling a cavity of thesaw body with the liquid by passing the cavity immediately adjacent therecessed area, and transporting the liquid away from the recessed areaby continuing to move the cavity from the recessed area towards thecutting area. The transported liquid passes from the cavity when thecavity moves beyond the bearing surface as a result of air turbulenceand inertial forces, and the liquid is consequently distributed both tothe saw body of the blade as well as to the cutting area thereofincluding the carbide insert teeth of the saw blade.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Other features and advantages of the present invention willbecome apparent to one having ordinary skill in the art in view of thefollowing disclosure of the preferred embodiment of the presentinvention and with reference to the drawings, in which:

[0015]FIG. 1 is a perspective partial view of a saw arrangement of thepresent invention including a plurality of circular saw blades andlubricating guide support assemblies therefor;

[0016]FIG. 2 is a perspective partial view of a guide support of a guidesupport assembly of FIG. 1;

[0017]FIG. 3 is a plan view of a circular saw blade of FIG. 1;

[0018]FIG. 4 is an additional plan view of the circular saw blade ofFIG. 3; and

[0019]FIG. 5 is an enlarged view of a section of the circular saw bladeof FIG. 3 including a cavity of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0020] Referring now to the drawings, the present invention relatesbroadly to a saw arrangement 8 including the combination of a circularsaw blade 10 and a lubricating guide support assembly 12. As shown inFIG. 1, this combination can be repeated to form what is commonly knownas a horizontal gang saw 14 in the lumber industry. In each combination,and with reference to FIG. 3, the saw blade 10 includes a cutting edge16 comprised of carbide insert teeth 18 for cutting during rotation ofthe saw blade 10. The saw blade 10 also includes a central opening 20 bywhich the saw blade 10 is mounted to an arbor 22 extending along an axis24 that simultaneously drives each saw blade 10 by rotation in acircumferential direction ω. The rotation of the saw blades 10 generatesthe cutting action of the gang saw 14 for the cutting of lumber in acutting area (generally indicated at 26).

[0021] Preferably each circular saw blade 10 includes a planar saw body28 having a diameter of 18½ inches and a thickness in an axial directionof 0.080 inches or less. Furthermore, each planar saw body 28 preferablydefines three liquid transport cavities 30 therein which extend entirelythrough the axial extent of the saw body 28 from a first planar surface32 thereof to a second planar surface 34 thereof. Moreover, the threecavities 30 are preferably equally spaced from the others around theaxial center of the saw body 28, i.e., spaced 120 degrees apart. Eachcavity 30 is also triangular in cross-section in the embodiment shown,but other shapes are equally applicable.

[0022] Regardless of the actual cross-sectional shape of the cavity 30that is used, the cavity 30 preferably includes a radial dimension ρthat varies along a circumferential direction θ of the circular sawblade 10 between opposed circumferential ends 36,38 of the cavity 30 asshown in FIG. 5. The radial dimension ρ also preferably exceeds 0.015inches whereby the cavity 30 has sufficient dimension to readily receiveliquid therein; it is noted that the laser cut slots of Carter Jr. U.S.Pat. No. 4,776,251 have a radially dimension less than 0.015 inches and,therefore, are of an insufficient width to receive liquid from therecessed area (just as sawdust packing is avoided by such a smallwidth).

[0023] Each cavity 30 in the present invention also preferably includesrounded corners 40 each having a radius of, for example, {fraction(3/16)} of an inch. A trailing edge 42 of the cavity 30 is alsopreferably oriented at a negative angle α of preferably 5 degrees withrespect to a radius R of the saw blade 10. These design configurationsfor the cavity 30 of the present invention prevent sawdust packing andenhance liquid distribution to the saw body 28 and cutting area 26 asdiscussed in detail below.

[0024] The lubricating guide support assembly 12 includes a plurality ofguide supports 44. As shown in FIG. 2, each guide support 44 includes abearing surface 46 disposed immediately beside an adjacent saw blade 10for proper alignment and support of the saw blade 10 during cutting.Each guide support 44 also includes a separate bearing surface 46 foreach adjacent saw blade 10. Furthermore, each bearing surface 46generally is spaced approximately 0.002 inches from an adjacent saw body28 when no cutting is being performed.

[0025] The guide support 44 includes a liquid lubricating systemcomprising a recessed area 48 extending within the guide support 44between bearing surface 46 thereof. The recessed area 48 is filled witha liquid under a pressure of approximately 35 psi that is exposed to theadjacent saw bodies 28, whereby a thin film of liquid is applied to eachsaw body 28 as it passes by the recessed area 48 during rotation of thesaw blade 10. As illustrated by the square area 49 of FIG. 4corresponding to an area of the saw body 28 exposed to the liquid in therecessed area 48, the recessed area 48 preferably covers in one rotationof the saw blade 10 a large portion of an annular section of the sawbody defined by dashed lines 50 thus providing for wide coverage of thesaw body 28. The liquid is pumped under pressure to the recessed area 48through passageways 52 and the liquid itself generally comprises anoil/water mixture, the oil being used for lubrication and the waterbeing used for cooling.

[0026] It has been determined by experiment that the total opening areaof the cavities 30 preferably should minimally approximate 6% of a“cutting triangle” of the circular saw blade 10. As illustrated in FIG.3, the cutting triangle 54 is an approximate right triangle having anarc 56 of the cutting edge 16 as a hypotenuse. In particular, the arc 56extends between a first vertex 58 defined by the point where a carbideinsert tooth enters the cant, and a second vertex 60 defined by thepoint where another carbide insert tooth simultaneously exits the cant.A first leg 62 lies along a bedplate 64 of the saw arrangement 8 andincludes the first vertex 58, and a second leg 66 lies perpendicular tothe bedplate and includes the second vertex 60. In the circular sawblades 10 of the drawings each cavity 30 is preferably identical to theothers and includes an opening area approximately equal to 2% of thearea of the cutting triangle 54.

[0027] Operation of the saw arrangement 8 and circular saw blade 10 ofthe present invention will now be described.

[0028] During rotation of the arbor 22, each saw blade 10 of the gangsaw 14 is simultaneously rotated while liquid is delivered underpressure into the recessed area 48 of each guide support 46. Therotation of the saw body 28 past the recessed area 48 and thedisposition of the bearing surface 46 of each guide support 44immediately adjacent the saw body 28 in conjunction with the pressurizedliquid in the recessed area 48 results in a thin film of liquidinitially being applied to the annular section defined by the dashedlines 50 shown in FIG. 4.

[0029] Each cavity 30 is formed in each saw body 28 in this annularsection defined by dashed lines 50 whereby each cavity 30 will pas bythe recessed area 48 during rotation of the saw blade 10 as illustratedin FIG. 3. As the cavity 30 passes by the recessed area 48 thepressurized liquid is driven into the cavity 30 and transported awayfrom the recessed area 48 toward the cutting area 26. Once the cavity 30clears the bearings surface 46 of the guide support 44, air turbulenceand inertial forces cause the transported liquid to pass out of thecavity 30 for distribution to the saw body 28 and the cutting area 26including the cutting edge 16 of the saw blade 10 both before and withinthe cant. The distribution of liquid to the saw body 28 and to thecutting area 26 is thereby increased as opposed to simply applying aliquid film to the annular section define by dashed lines 50.

[0030] The design configurations of each cavity 30 set forth aboveenhance this liquid distribution and prevent sawdust packing. Inparticular, due to the radial variance of ρ in the dimension of thecavity 30, the cavity 30 is narrower at the leading point first 68passing by the recessed area 48 and grows radially largercircumferentially along the saw body 28. This narrow-to-wide transition,in conjunction with the rounded corners 40 and negative angle α of thetrailing edge 42 of the cavity 30, draws the liquid into the cavity 30and, when the cavity 30 clears the bearing surface 46, draws air intothe cavity 30 displacing the liquid carried therein out of the cavity 30in what is believed to be a vortex or swirling action. It has also beenobserved that the trailing edge 42, because of its angled orientation tothe radius R of the blade 10, enhances distribution of the liquid towardthe center of the saw body 28 before inertial forces draw the liquid ina direction from the center of the saw body 28 towards the cutting edge16. Moreover, during its pass through the cant, sawdust is driventowards the angled trailing edge 42 and is deflected thereby withoutfinding niches to accumulate within, especially since the corners 40 ofthe cavity 30 are rounded. Thus, among other benefits of the presentinvention, sawdust packing is avoided without unduly limiting the radialdimension ρ of the cavity 30 to a constant value less than 0.015 inchesas taught by Carter Jr. Moreover, it is noted that a narrow slot asdisclosed by Carter Jr. would not draw the required liquid therein whilepassing by the recessed area 48 of the present invention.

[0031] In specific comparison of the saw arrangement against thelubricating guide blocks of McGehee and a saw blade as taught by CarterJr., Applicant has found that the saw arrangement 8 of the presentinvention is clearly superior. In particular, following cutting oflumber from Southern Yellow Pine, a layer of liquid along the cut lumberand relatively cool sawdust both were observed using the saw arrangement8 of the present invention, but no liquid layer and relatively hotsawdust both were observed using the saw blade of Carter Jr. with thelubricating guide blocks of McGehee. Carbide teeth breakage was alsoencountered using the saw blade of Carter Jr. with the lubricating guideblocks of McGehee, but was not encountered under identical circumstancesusing the saw arrangement 8 of the present invention.

[0032] The saw blade 10 of the present invention also exhibits easiermaintenance than other conventional saw blades. In particular, therounded corners 40 and size of each cavity 30 allow for easier clean outand reshaping of the cavity 30 by a saw filer. For instance, the heatingand cooling of the saw blade 10 causes the area of the saw body 28defining the cavities 30 to harden, becoming brittle and cracking overtime. By further rounding the cavities 30, the saw filer is able to fileaway these hardened areas without significantly altering the shape ofthe cavity 30. The filer can also refurbish openings defining thecavities 30 where the edges have been worn by friction, maintaining theintegrity of the saw body 28 and the effectiveness of the liquidtransporting capabilities of the cavities 30.

[0033] Another benefit of the present invention over conventional sawarrangements including liquid lubrication guide supports such as thatdisclosed in McGehee is the reduction in the accumulation time of theliquid within the recessed area 48 due to the additional removal of theliquid from the recessed area 48 by the cavities 30. Reduction of thetime of the liquid within the recessed area 48 reduces the time in whichthe liquid within the recessed area 48 is thermally exposed to the guidesupport 44 and subjected to heat transfer via convection resulting fromthe abutment between each bearing surface 46 with an adjacent saw body28.

[0034] In sum, the liquid transport cavities of the present inventionachieve a degree of cooling not obtained by the aforementionedconventional saw arrangements and provide greater operating life andeasier and less maintenance than that of other conventional saw blades.Furthermore, the improved cooling benefits of the present inventionfurther the attempt to reduce saw blade thickness below the currentfloor of 0.080 inches for saw blades used with guide supports to cutlumber from Southern Yellow Pine.

[0035] It will therefore be readily understood by those persons skilledin the art that the present invention is susceptible of broad utilityand application. Many embodiments and adaptations of the presentinvention other than those herein described, as well as many variations,modifications and equivalent arrangements, will be apparent from orreasonably suggested by the present invention and the foregoingdescription thereof, without departing from the substance or scope ofthe present invention. Accordingly, while the present invention has beendescribed herein in detail in relation to its preferred embodiment, itis to be understood that this disclosure is only illustrative andexemplary of the present invention and is made merely for purposes ofproviding a full and enabling disclosure of the invention. The foregoingdisclosure is not intended or to be construed to limit the presentinvention or otherwise to exclude any such other embodiments,adaptations, variations, modifications and equivalent arrangements, thepresent invention being limited only by the claims appended hereto andthe equivalents thereof.

[0036] Thus, it will be apparent, for example, that the liquidpassageways of the guide supports could deliver the liquid underpressure directly to the saw body in the manner of liquid ports formingthe recessed area of the guide supports, with the liquid transportcavities passing by the liquid ports for receipt of liquid directlytherein. The cavities also do not have to extend entirely through thesaw body, although better distribution of the liquid carried therein tothe saw body and the cutting area is achieved when air turbulence passesthrough the saw body. Moreover, the configuration of the cavity need notbe triangular in cross-section nor have only rounded corners therein. Itis only a requirement that the cavities be of sufficient area anddimension to receive a quantity of liquid therein from the guidesupports as it passes thereby for delivery to the saw body and cuttingarea. It should also be apparent that while a horizontal gang saw hasbeen used to illustrate the preferred embodiment of the presentinvention, the present invention is equally applicable to vertical gangsaws or to single blade rip saws, whether vertically or horizontallydisposed.

1. A saw arrangement comprising the combination of: a saw bladeincluding a saw body defining a plurality of cavities therein, and acutting edge disposed along a periphery of said saw body for cuttingduring movement of said saw blade, each one of said cavities beingdisposed entirely within an annular section of said saw body andcompletely bounded by said saw body thereby isolating said cavity fromsaid cutting edge; and a lubricating guide support having a bearingsurface disposed immediately adjacent said saw body for proper alignmentof said saw blade during cutting, said guide support containing liquidexposed to said saw body at said bearing surface whereby the liquid isapplied to said saw body as it passes by said bearing surface duringmovement of said saw blade, each one of said cavities arranged on saidsaw body to pass by said exposed liquid during movement of said sawblade and dimensioned to receive liquid therein for transport of theliquid away from said bearing surface.
 2. A saw arrangement according toclaim 1 , wherein each one of said cavities includes a radial dimensiongreater than 0.015 inches sufficient to receive liquid therein fortransport of the liquid away from said bearing surface.
 3. A sawarrangement according to claim 1 , wherein said saw body has a thicknessno greater than 0.080 inches.
 4. A saw arrangement according to claim 1, wherein each one of said cavities extends through said saw body from afirst side thereof to a second, opposite side thereof.
 5. A sawarrangement according to claim 1 , wherein each one of said cavities istriangular is cross-section.
 6. A saw arrangement according to claim 1 ,wherein said plurality of cavities comprise three cavities spaced 120degrees to one another about a center of said saw body.
 7. A sawarrangement according to claim 1 , wherein each one of said cavitiesincludes a radial dimension that varies along a circumferentialdirection of said saw body between opposed circumferential ends of saidcavity.
 8. A saw arrangement according to claim 1 , wherein each one ofsaid cavities includes corners all of which are rounded.
 9. A sawarrangement according to claim 1 , wherein said bearing surface isdisposed approximately 0.002 inches from said saw body.
 10. A sawarrangement according to claim 1 , wherein each one of said cavities hasa triangular cross-section, a trailing edge of which is oriented atnegative 5 degrees to a radius of the saw body.
 11. A method for cuttinglumber from Southern Yellow Pine including the steps of providing a sawarrangement including a circular saw blade and lubricating saw guides,the circular saw blade including a planar saw body having an axialthickness less than 0.080 inches and defining a plurality of cavitiestherein each having a radial dimension that varies along acircumferential direction of said circular saw body between opposedcircumferential ends of said cavity; and cutting the Southern YellowPine into lumber using said saw arrangement.
 12. The method of claim 11, wherein each one of said cavities includes a radial dimension greaterthan 0.015 inches sufficient to receive liquid therein for transport.13. The method of claim 11 , wherein each one of said cavities extendsthrough said planar saw body from a first side thereof to a second,opposite side thereof.
 14. The method of claim 11 , wherein each saidcavity is triangular in cross-section.
 15. The method of claim 11 ,wherein said plurality of cavities comprises three cavitiesconsecutively spaced 120 degrees apart with respect to a center of saidcircular saw blade.
 16. The method of claim 11 , wherein each one ofsaid cavities includes corners all of which are rounded.
 17. The methodof claim 11 , wherein said saw blade is disposed approximately 0.002inches from a said saw guide.
 18. The method of claim 11 , wherein eachone of said cavities has a triangular cross-section, a trailing edge ofwhich is oriented at negative 5degrees to a radius of the saw body. 19.A circular saw blade for cutting lumber from Southern Yellow Pine,comprising a planar saw body having an axial thickness no greater than0.080 inches and defining a plurality of cavities therein, each one ofsaid cavities: a) extending through said saw body from a first sidethereof to a second, opposite side thereof b) having a triangularcross-section with generally rounded corners and a trailing edgeoriented at an approximate negative 5 degrees to a radius of the sawbody, and c) including a radial dimension greater than 0.015 inches thatvaries along a circumferential direction of said circular saw bodybetween opposed circumferential ends of said cavity sufficient toreceive liquid therein for transport.
 20. The circular saw blade ofclaim 20 , wherein said plurality of cavities comprise three cavitiesconsecutively spaced approximately 120 degrees apart with respect to acenter of said saw blade.